Using Styrofoam balls and a light bulb, students explore how the phases of the Moon arise and why they change. Research has shown that students will cling to previous misconceptions about the reasons for moon phases, even after hearing the correct explanation. This activity not only demonstrates the actual reason for moon phases but also helps students visualize the geometry of Earth's orbit and the orbits of the Sun and the Moon.

Why Should My Students Do This?The most common misconceptions that students have about the moon phases--such as clouds block the Moon as well as Earth's shadow covers the Moon--are reasonable, but don't hold up under careful observation of the Moon. Once students are confronted with the inconstancies of their private theories, they can do activities such as this one to adopt alternative explanations.

What's Good about This Activity? Like many concepts in astronomy, the correct explanation of moon phases is abstract, difficult to express in words, and exacting of students to possess strong three-dimensional spatial reasoning skills. This activity not only demonstrates the reason for moon phases but also helps students develop spatial perception as they create a mental image of the motions of the Sun, the Moon, and Earth.